Help me understand Steering Wheel Controls

Hi Guys,

I'm trying to make a Steering Wheel Interface for my Bluetooth kit... and there's a possibility I could make this something that others could use.

I just need a start in the right direction and you guys seem knowledgeable on the subject - would appreciate your help as Google isn't giving me the answer. With resistive steering wheel controls, am I right in thinking there are two types of doing it?